August 02, 2017

Imagine getting into a crowded Mumbai local during peak hours. Thousands of people on the platform along with you and hundreds inside the train. You got to get into the train to reach home in time. You experience people pushing you from behind, making it difficult to get in comfortably. The train folks are resisting you from getting into the already crowded compartment. If think of yourself as the electric signal who has to get into the train and reach a destination to be converted into music, then the difficulty and resistance that you’ll have to face throughout the entire journey can be construed as resistance.

 Impedance is the Resistance and so from this example we can understand from impedance is.

If you hated Physics, let me throw a physics bomb your way, because we’re sadistic that way.

Resistance(R) is the opposition to Current (I) on every applied Voltage. If you can recollect Ohm’s law from high school physics, it said V=IR. That means R=V/I.

Now comparing to the train example, there were two resisting factors, people pushing from outside and inside. The total amount of Resistance you face from outside and inside is the Impedance. Impedance, like Resistance, is measured in ohms.

How the hell does this matter while using a headphone you ask, (through teary eyes, we imagine)? It does, a lot. As you know, headphones have driver units, the speakers that provide the audio output. These speakers have magnets that help generate sound in the headphone. These magnets require current to run. Where there is current, there is impedance, resistance and all it’s brethren that we mentioned above (evil laugh). Simply put, the circuit in question, the one containing the driver and magnets and all, will require current to function. Though it needs current to run, the circuit will provide an overall resistance to the current trying to run through it. The amount of current required to overcome this impedance and generate the electricity required to power the speakers. Capiche?

When it comes to headphones, have you ever wondered why impedance plays an important role? Headphone is just a smaller speaker for you to listen to personally. Knowing the impedance of a pair of headphones will answer questions like:

  1. Can I use my headphones with my smart phone?
  2. Do I need an amp for my headphone?

 

It is important to address these questions because if you don’t provide the right amount of current, your beautiful looking headphones won’t perform at their optimum best.

Loudspeakers need to give huge output, so their impedance is mapped at 4, 6 or 8 ohms. Headphones being smaller and needing lesser sound output have impedance ranging from 15 to 35 ohms, in general.

As explained most earphones and headphones compatible with phone or computer have impedance in this range. This limits the audio output to stay under 1000mW. This is more than enough for portable headphones.

What about the headphones having higher impedance? Why can’t they be used with mobile devices?

Simple, your phone and laptop don’t have the power to power those headphones.

Thus, amplification comes into the picture here. What do you do when a door won’t open? Simply apply more force. Amplification is required for headphone drivers having impedance above 35 ohms.

There are different amplifiers made to match headphones of that impedance to get the proper amplified output.

Why the need for higher impedance? Why the need for headphone amplifiers?

The relation between impedance and loudness is inversely proportionate. Lesser the impedance, higher the output volume. This is not always the case when considering quality of output as fidelity is a different aspect.

 

There’s a notion that higher the impedance better the audio quality.  This statement is not always true. Headphones having 35 ohms impedance are also used in professional setups too.. How to justify this statement?

Speaker drivers having higher impedance are made up of better materials. This may give better audio quality when playing high quality audio files. It helps maintain the Audio fidelity, making the audio sound more original. Another reason professional and audiophile headphones have high impedance is to protect them from actually blowing up when connected to high power sources. DJ turntables, Audio Mixers, Audio boxes have powered jacks, which may cause harm to low impedance headphones.

Do you get it now? Why there are headphones and earphones having different impedance levels?

Let’s simplify it, What do you need?

If you are listening to music from a portable device like mobile phone, laptop, ipod and other players, all you need is a earphone or headphone having low impedance.

If you are a professional or audiophile, i don’t need to tell you. High impedance Headphones of course. Music is what matters at last.

Take an Audeze LCD-X and try listening to it by plugging it into a laptop or PC. Now the impedance of the headphone is mapped at 100 ohms while the output of the PC port is as low as 32 ohms. It’s clearly not powerful enough to match the impedance of the headphone. Sure you might hear some music playing on the headphone but it’ll hardly be impressive. You might even wonder if you’ve been given a fake one, especially for the price you’ve paid! Throw in a Schiit Magni 2 which will supply the necessary juice needed. Now, try again. The headphone will definitely show a remarkable change in output.


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